The present invention relates to a fuel injection control device for diesel engines. More particularly, the invention is concerned with a fuel injection control device for automotive diesel engines, capable of preventing overheating of diesel engine, in spite of generally inferior cooling condition, without substantially impairing the running performance of the automobile and without requiring suspension of operation of auxiliary equipments such as air conditioner driven by the engine.
Diesel engines generally exhibit a high thermal efficiency thanks to a high compression ratio, but the thermal efficiency is not so high in the full-load operation. Unfortunately, it is becoming difficult to find sufficient space in the engine room for mounting cooling system including a radiator for automotive diesel engine, due to current tendency such as mounting of a supercharger or turbocharger for increasing the engine output for a given engine displacement, slanting of the nose or front end of the automobile for improving the aerodyamical performance of automobile, and so forth. Therefore, the diesel engines are apt to be overheated due to insufficient cooling particularly in current automobiles.
Various proposals have been made hitherto for overcoming the problems concerning insufficiency of the cooling. For instance, in some diesel engines, the rate of fuel injection, i.e. the rate of delivery of fuel from a fuel injection pump to fuel injection nozzles, is decreased when the temperature of a coolant for cooling the engine is raised to a predetermined temperature, thereby to prevent overheating of the engine. It has been proposed also to stop the operation of air conditioner connected to the engine when the predetermined coolant temperature is reached.
These measures, however, suffer from the following disadvantages. Namely, if the rate of fuel injection is decreased, the output power of the engine is also decreased to reduce the speed of the automobile particularly when the latter is running along an ascending slope. In the worst case, the automobile may become unable to ascend the slope. On the other hand, the suspension of operation of the air conditioner inconveniently raises the air temperature in the automobile to impose an uncomfortable feel on the driver and passengers.